1. Field of the Invention
The present invention relates generally to the field of biology and medicine. More particularly, the present invention relates to feline pancreatic lipase compositions, methods for preparing such compositions, and methods for employing such compositions to detect the concentration of pancreatic lipase in cat serum for diagnosis and management of pancreatitis.
2. Description of Related Art
Lipases are water-soluble enzymes that hydrolyze water-insoluble substrates into more polar lipolysis products (Petersen and Drabløs, 1994). In 1856 Claude Bernard identified the first lipase (Petersen and Drabløs, 1994). Since then a plethora of lipases has been identified in microorganisms, plants, and animals (Lin et al., 1986; Jaeger et al., 1994; Petersen and Drabløs, 1994; Mukherjee and Hills, 1994; Lawson et al., 1994). Lipases share a common triad of amino acids (serine, aspartic or glutamic acid, and histidine) in the active site, which is also shared with serine proteases (Svendsen, 1994). Another common feature of almost all lipases are glycosylation site motifs (Antonian, 1988). Many lipases have been shown to be related phylogenetically. The pancreatic lipase gene family is a large gene family with 9 subfamilies (Petersen and Drabløs, 1994; Carrière et al., 1997; Carrière et al., 1998; Hirata et al., 1999). In addition there are other groups of phylogenetically related lipases, and yet other lipases that do not belong to a defined gene family (Anderson and Sando, 1991).
The main function of lipases is the hydrolysis of lipids. A lipase is needed whenever an apolar lipid needs to cross a biological membrane. Triglycerides are prime examples of apolar lipids. Thus lipase is needed in order for triglycerides to be absorbed from the intestinal tract. There are two digestive lipases in most vertebrate species, i.e., a preduodenal lipase and classical pancreatic lipase (Carrière et al., 1994). In addition, in neonates, lipase for digestion of triglycerides is also supplied through milk (Freed et al., 1986; Freed et al., 1987). This lipase is known as bile salt-stimulated lipase (Freed et al., 1986; Freed et al., 1987). Even though it is crucial for the digestion of triglycerides in milk, bile salt-stimulated lipase is not considered as a digestive lipase, as it is not utilized as a digestive lipase in the organism where it was synthesized. Preduodenal lipase has been shown to originate from a single tissue in all species examined to date (Moreau et al., 1988). A pharyngeal lipase was identified in cows and sheep, a lingual lipase in rats and mice, and a gastric lipase in human beings, monkeys, horses, pigs, guinea pigs, cats, and dogs (Moreau et al., 1988). No preduodenal lipase could be identified in chickens (Moreau et al., 1988). In human beings and dogs it has been shown that gastric lipase contributes significantly to the digestion of dietary triglycerides (Carrière et al., 1993a; Carrière et al., 1993b). However, pancreatic lipase (also called classical pancreatic lipase) is the most important enzyme in the digestion of dietary triglycerides (Carrière et al., 1991; Carrière et al., 1993a).
It has recently been shown by immunolocalization that pancreatic lipase is only present in pancreatic acinar cells in clinically healthy dogs, suggesting that classical pancreatic lipase may be an ideal marker for function and pathology of the exocrine pancreas (Steiner et al., 2002). This hypothesis has been confirmed in clinical studies that have shown that the measurement of pancreatic lipase immunoreactivity in serum is a specific marker for exocrine pancreatic function and also highly sensitive for pancreatitis in the dog (Steiner et al., 2001a; Steiner et al., 2001b; Steiner et al., 2001c). The purification of classical pancreatic lipase has been reported in many species (Vandermeers and Chroistophe, 1968; Rathelot et al., 1981; Bosc-Bieme et al., 1984; Gieseg et al., 1992; Mejdoub et al., 1994; Steiner and Williams, 2003). However, the purification of feline classical pancreatic lipase has not been reported previously.
Pancreatitis is a common gastrointestinal disorder in cats and is characterized by the autodigestion of the exocrine pancreas. Clinical symptoms of feline pancreatitis are non-specific and the disease can be difficult to diagnose. Pancreatitis is associated with an increased amount of digestive enzymes and zymogens leaking into the blood stream. One of these enzymes is pancreatic lipase. A number of assays have been developed to detect the presence of lipase in serum by use of catalytic assays. However, these assays lack both sensitivity and specificity for pancreatitis in both human beings and dogs. Furthermore, these assays for the quantification of lipase activity have been shown to have no clinical utility in the diagnosis of feline pancreatitis.
Therefore, there is a long-standing need for an effective method to prepare and purify feline pancreatic lipase as well as an effective method to diagnose feline pancreatitis.